The present invention relates to a water-repellent glass panes which are usable for architectural, automotive, watercraft and aircraft windows, and methods for producing such glass panes.
Recently, there is a demand for water-repellent glass panes which are superior in durability and water repellency for a long time. In general, a water-repellent glass pane is produced by forming a water-repellent thin film on a glass substrate. There is known sol-gel process for forming a water-repellent thin film and other various functional thin films on glass substrates. In this process, a raw material of the film is mixed with a suitable solvent and water. Due to this mixing, the raw material is subjected to hydrolysis and then to dehydration and polycondensation. With this, the resultant mixture turns into a sol. Then, this sol is applied to a glass substrate, thereby to form thereon a precursory film. Then, the precursory film is dried and then optionally heated, thereby to form thereon a functional thin film. With this step, water and/or alcohol is removed from the precursory film.
Japanese Patent Unexamined Publication JP-A-57-181091 teaches the use of a dehydrator for removing water formed as a by-product, in the production of cyclic methyl(1-trifluoromethylethyl)polysiloxane represented by a general formula (I) disclosed therein.
JP-A-5-96679 discloses a water-repellent, oil-repellent monomolecular film. This film is chemically bonded to the surface of a substrate by a covalent bond containing xe2x80x94Sixe2x80x94 group and is formed of molecules of at least two types having different molecular chain lengths.
JP-A-9-132433, which has an application number of 7-294106, discloses a water-repellent glass pane. This glass pane has a glass substrate, a first metal oxide thin film directly formed on the glass substrate, and a second water-repellent thin film formed on the first film. The first film is prepared by a sol-gel process and has a minutely rough surface. In the preparation of the first film, a particular sol is applied to the surface of the glass substrate in an atmosphere of 25xc2x0 C. and a relative humidity of from 45 to 70%.
JP-A3-247537 discloses a method for producing a water-repellent glass plate. This method comprises sequential steps of (a) abrading a surface of a glass substrate by using a abrasive powder, while the surface is washed; (b) forming thereon a precursory film by applying a silicone-based water-repellent agent thereto; and (c) curing the precursory film into a water-repellent film having a thickness of from 0.1 to 2 xcexcm. The water-repellent agent is prepared by replacing at least 5% of hydrogen atoms of alkyl group of polydialkylsiloxane with fluorine atoms.
JP-A-58-122979 discloses in Example 1 a method for forming a water-repellent, oil-repellent thin film on a glass substrate. In this method, a glass substrate is washed with a detergent and acetone, then is immersed in a 1% hydrochloric acid solution, and then is dried. Then, a particular coating liquid is applied to the surface of the glass substrate. Then, the obtained thin film formed on the glass substrate is cured at 120xc2x0 C. for 20 minutes in an atmosphere of a relative humidity of 100%. JP-A-58-129082 discloses in Example 1 another method for forming a water-repellent, oil-repellent thin film on a glass substrate. This method is the same as that of JP-A-58-122979, except in that the coating liquid composition is different from that of JP-A58-122979 and that the curing temperature is 160xc2x0 C., in place of 120xc2x0 C.
It is an object of the present invention to provide a water-repellent glass pane having a water-repellent film armed on a glass substrate, which film is superior in abrasion resistance, sunshine resistance, hardness, adhesion to the glass substrate, and water-repellency for a long time.
It is another object of the present invention to provide a method for producing such water-repellent glass pane, which method is superior in safety, simplicity and efficiency.
According to a first aspect of the present invention, there is provided a water-repellent glass pane having a glass substrate and a water-repellent film formed on the glass substrate. This glass pane is prepared by a first method comprising sequential steps of:
(a) mixing together a raw material for producing said water-repellent film, an organic solvent for diluting said raw material, and water for hydrolyzing said raw material, such that said raw material is subjected to hydrolysis and then to dehydration and polycondensation, thereby to turn a mixture of said raw material, said organic solvent and said water into a sol;
(b) adjusting water content of said sol, thereby to prepare a coating liquid; and
(c) applying said coating liquid to said glass substrate, in an atmosphere having a first temperature aid a relative humidity.
According to the first aspect of the present invention, there is prepared by the step (b) a coating liquid wherein the degree of polycondensation of the raw material is high and stable. Due to the application of this coating liquid to a glass substrate, there is formed on the glass substrate a water-repellent film which is superior in abrasion resistance, sunshine resistance, hardness, adhesion to the glass substrate, and water-repellency for a long time.
According to a second aspect of the present invention, there is provided a water-repellent glass pane having a glass substrate and a water-repellent film formed on the glass substrate. This glass pane is prepared by a second method comprising sequential steps of:
(a) subjecting a surface of said glass substrate to an abrasive treatment;
(b) subjecting said surface of said glass substrate to an acid treatment; and
(c) applying a coating liquid to said surface of said glass substrate.
According to the second aspect of the present invention, it becomes possible by the step (a) to substantially completely remove stains and scales of the glass substrate""s surface and a very thin glassy layer formed on the glass substrate""s surface, such as a silica-rich layer formed on the surface of a curved glass and/or tempered glass. Furthermore, advantageous effects of the step (b) are enhanced by the step (a). By the acid treatment of the step (b), silanol groups are effectively formed on the glass substrate""s surface. These silanol groups contribute to increase the water-repellent film in adhesion to the glass substrate.
In the present invention, it is optional to combine the above-mentioned first and second aspects of the present invention. In other words, the coating liquid prepared in accordance with the steps (a) and (b) of the first method of the first aspect may be applied to the glass substrate prepared in accordance with the steps (a) and (b) of the second method of the second aspect, in the atmosphere of the step (c) of the first method of the first aspect.